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Abstract:

An absorbent article such as a diaper, panty diaper, panty liner, sanitary
napkin or incontinence device, wherein at least one part of the absorbent
article carries a film having at least one monomolecular layer of a
polymer having a functional group and an active agent, in particular to
an absorbent article wherein the film is obtainable by layer-by-layer
deposition of at least a first polymer having a first functional group
and a second polymer having a second functional group capable of
interacting with the first functional group. Moreover, the use of a film
obtainable by the layer-by-layer deposition of at least one first polymer
having a first functional group and a second polymer having a second
functional group capable of interacting with the first functional group
for releasing an active agent contained in the film upon wetting of the
film by body fluids. Preferably the first polymer having a first
functional group is a polycationic polymer and the second polymer having
a second functional group is a polyanionic polymer.

Claims:

1. An absorbent article, wherein at least one part of said absorbent
article carries a film comprising at least one monomolecular layer of a
polymer having a functional group and an active agent.

2. The absorbent article according to claim 1, wherein the film is
obtainable by layer-by-layer deposition of at least a first polymer
having a first functional group and a second polymer having a second
functional group capable of interacting with the first functional group.

3. The absorbent article according to claim 1, wherein the film is
comprised of 2 or more layers.

4. The absorbent article according to claim 1, wherein the film has a
thickness below 1 μm.

5. The absorbent article according to claim 1, wherein the functional
group is selected from polar groups.

6. The absorbent article according to claim 2, wherein the interaction
between the first functional group and the second functional group is
selected from electrostatic attraction, donor/acceptor interaction,
hydrogen bonding and specific recognition.

7. The absorbent article according to claim 1, wherein the active agent is
an odour-controlling agent or a skin care agent.

8. The absorbent article according to claim 7, wherein the skin care agent
is selected from naturally occurring active agents or mixtures thereof.

9. The absorbent article according to claim 7, wherein the
odour-controlling agent is selected from bacteriostatic or bactericidal
agents, pH control agents, odour-absorbing particles, odour-decomposing
catalysts and odour-masking compounds.

10. The absorbent article according to claim 2, wherein the first polymer
is a polycationic polymer and the second polymer is a polyanionic
polymer.

11. The absorbent article according to claim 10, wherein the polycationic
polymer is selected from cationic or cationically modified
polysaccharides, polyallylamine homo- or copolymers, polyvinylamines
homo- or copolymers and polyethylenemine.

13. The absorbent article according to claim 10, wherein the film
comprises at least one polycationic, at least one polyanionic polymer and
a charged active agent.

14. The absorbent article according to claim 13, wherein the charged
active agent is selected from the group consisting of odor controlling
agents and skin care agents.

15. The absorbent article according to claim 2, wherein the first polymer
is a hydrogen bond donor polymer and the second polymer a hydrogen bond
acceptor polymer.

16. The absorbent article according to claim 15, wherein the hydrogen bond
donor polymer is selected from polycarboxylic acid, a polynucleotide, a
polymer of vinylnucleic acid, a polyaminoacid, a polyalcohol and a
copolymer thereof.

17. The absorbent article according to claim 15, wherein the hydrogen bond
acceptor polymer is selected from a polyether, polyketone, a
polyaldehyde, a polyacrylamide, other polyamides, a polyamine, a
polyurethane, a polyester, a polyphosphazene or polysaccharide and a
copolymer thereof.

18. The absorbent article according to claim 15, wherein the film
comprises at least one hydrogen bond donor polymer, at least one hydrogen
bond acceptor polymer and an active agent comprising at least one
hydrogen bond donor and/or acceptor moiety.

19. The absorbent article according claim 18, wherein the active agent
comprises at least one hydrogen bond donor or an acceptor moiety, and is
selected from the group consisting of odor controlling agents and skin
care agents.

20. The absorbent article according to claim 2 wherein at least one layer
is a layer of inorganic particles or other charged active agents.

21. The absorbent article according to claim 20, wherein the particles are
selected from bacteriostatic or bactericidal metal particles,
odour-decomposing metal particles and odour absorbing particles.

22. The absorbent article according to claim 2, wherein the film
obtainable by layer-by-layer deposition comprises at least one
bacteriostatic or bactericidal polycationic polymer as an active agent
and is present as an upper layer of said film.

23. The absorbent article according to claim 22, wherein the
bacteriostatic or bactericidal polycationic polymer is chitosan.

24. The absorbent article according to claim 10, wherein the active agent
comprises bacteriostatic or bactericidal metal ions such as silver ions
or bacteriostatic or bactericidal metal particles such as silver
particles dispersed through at least a part of the film.

25. The absorbent article according to claim 1, wherein the part
comprising the film is selected from a topsheet, backsheet, layers
arranged between topsheet and the absorbent layer, fibers or particles, a
waistband and leg cuffs.

26. The absorbent article according to claim 25, wherein the absorbent
article is a diaper or incontinence device and the part thereof carrying
the film is selected from a topsheet, gasketing and/or front barrier
cuffs.

27. The absorbent article according to claim 1, wherein the part is
selected from a topsheet, gasketing or front barrier cuffs and is made
from a hydrophobic material and is subjected to corona or plasma
treatment prior to deposition of the film.

28. A method of making a film, the method comprising a layer-by-layer
deposition of at least one first polymer having a first functional group
and a second polymer having a second functional group capable of
interacting with the first functional group for releasing an active agent
contained in said film upon wetting of said film by body fluids.

29. The method according to claim 28, wherein the first polymer having a
first functional group is a polycationic polymer and the second polymer
having a second functional group is a polyanionic polymer.

30. The method according to claim 28 wherein the deposition is on a
carrier part of an absorbent article.

31. (canceled)

32. The method according to claim 28, wherein the body fluids are selected
from urine, watery feces, menstrual fluid and female secretion.

33. The absorbent article according to claim 14, wherein the part
comprising the film is selected from a topsheet, backsheet, layers
arranged between topsheet and the absorbent layer, fibers or particles, a
waistband and leg cuffs.

Description:

[0001]The present disclosure relates to an absorbent article such as a
diaper, panty diaper, panty liner, sanitary napkin, incontinence device
or the like wherein one part thereof includes an active agent. The
present disclosure relates in particular to such an absorbent article
wherein controlled release of the active agent is effected by a
nanoscalar film which is preferably obtained by layer-by-layer deposition
of at least two polymers having interacting functionalities.

TECHNICAL BACKGROUND

[0002]It is often desirable to provide absorbent articles of the
above-mentioned type with functions going beyond their capacity to absorb
and store body fluids such as urine or menstrual fluids. These functions
involve for instance a skin care effect or the suppression or prevention
of unpleasant odours.

[0003]Existing absorbent articles that show these additional functions
comprise active agents, which are either loosely bound to a diaper part
or embedded in a matrix being typically of lotion type (see for instance
WO 96/16682) or polymer type.

[0004]Loosely bound active agents suffer from the disadvantage that they
are too easily rubbed off or washed off under body motion or with the
first gush of urine. This may also occur if the active agent is fixed in
a lotion matrix. Polymer systems, on the other hand, are often not
capable of releasing active agents specifically when these are needed,
that is upon contact with body fluids. Moreover, relatively high amounts
of polymers or lotions are needed for an efficient embedding of the
active agent. Polymers and lotions can also adversely affect the
properties of the underlying substrate such as flexibility, softness,
absorbency, hydrophilicity, etc.

[0005]Moreover, nanoscalar films of self-assembling polymers are known
from various technical fields and have attracted considerable interest
over the last years. These nanoscalar films are typically formed by the
alternate deposition of monomolecular layers of two polymers having
functional groups capable of interacting with each other. A great deal of
these studies has been conducted with the layer-by-layer deposition (also
abbreviated as LBL deposition) of cationic and anionic polymers based on
the reversal of the surface charge after each deposition, one of the
best-examined systems being poly(styrene sulfonate)/(polyallylamine
hydrochloride)(PSS/PAH).

[0006]U.S. 2005/0069950 A1 discloses a method for the nanofabrication of
thin films, coatings and microcapsules based on suitable design of
oligopeptides. Drug delivery is discussed in connection with
microcapsules. Moreover, disposable diapers are mentioned as one among
many possible uses for peptides designed according to this documents.
More concretely described are biomedical applications.

[0007]U.S. Pat. No. 5,807,636, U.S. Pat. No. 5,700,559 and U.S. Pat. No.
5,837,377 relate to a hydrophilic article for use in aqueous environments
including a substrate, an ionic polymeric layer on said substrate and a
disordered polyelectrolyte coating ionically bonded to said polymeric
layer. Diapers and other liners are mentioned as one among many potential
applications of this teaching.

[0009]WO 00/32702 describes for instance a paper or nonwoven product
containing fibers, filler particles or other particles produced by the
layer-by-layer deposition of two interacting polymers, preferably anionic
and cationic polyelectrolytes, which are typically used as dry and wet
strength agents in the paper manufacture. Accordingly, this document also
evaluates the tensile strength of the paper product.

[0010]WO 2005/032512 relates to an article comprising a particle, a first
neutral polymer film and a second neutral polymer film which are
associated by hydrogen bonding between a hydrogen bond donor polymer,
such as polycarboxylic acid and a hydrogen bond acceptor polymer such as
polyether, polyketone, polyaldehyde, polyacrylamide, polyamine,
polyester, polyphosphazene or polysaccharide or a copolymer thereof. It
is stated that capsules as one embodiment of this article are useful to
deliver the core particle in a controlled and well-defined manner upon
exposure to external stimuli. Application areas mentioned in this
document are biotechnology, medicine, pharmaceuticals, foods,
agriculture, perfumery, personal care and cosmetics.

[0011]US 2004/0137039 A1 provides in one embodiment a method of releasing
low molecular weight polymers, such as drugs, dyes or other molecules
from a LBL polymer film having a net excess charge, by introducing to the
system at least one other type of molecule that binds reversibly to the
film and thereby reduces the net excess charge. A second embodiment
pertains to a method of selectively and reversibly releasing oligomeric
and polymeric molecules, such as natural and synthetic polypeptides,
oligo- and polynucleotides or other molecules having plurality of
charges, from a LBL film formed from these oligomeric and polymeric
molecules and a second polymer having the opposite charge, in response to
variation in pH or ionic strength.

[0013]US 2004/0047979 A1 describes an improved layer-by-layer-coating
process for modifying the surface of a medical device preferably an
ophtelmic device, more preferably a contact lense. Polyanionic and
polycationic polymers are employed for this layer-by-layer coating which
is said to increase the hydrophilicity of a medical device.

[0014]U.S. Pat. No. 5,885,753 discloses a self-assembled multilayer that
can be effectively produced from two or more self-assembled monolayers on
a substrate where each of the self-assembled monolayers is produced for a
block containing a first functional group and a second functional group
reacting with each other. Polymerized mono- or multilayer embodiments
thereof can be employed in a variety of applications including
photolithography.

[0015]WO 2004/07677 A2 relates to a continuous process for manufacturing
electrostatically self-assembled coatings. Under background of the
invention it is explained that such multilayer assemblies have found use
in applications for full color flat displays, membrane separation,
barrier coatings, corrosion control coatings, electrochromic coatings,
electroluminescent devices, conducting and insulating circuits, optical
and non-linear optical devices, solar cells, high strength composites and
multielement chemical sensors. According to preferred embodiments of this
method, layers of polycationic polymers and negatively charged inorganic
materials, such as platelet clays are arranged alternately in layers
having a thickness of about 1 nm.

[0016]U.S. Pat. No. 6,428,811 B1 relates to a thermally sensitised
polymer-particle composite that absorbs electromagnetic radiation and
uses the absorbed energy to trigger the delivery of a chemical. Metal
nanoshells are nanoparticulate materials that are suitable for use in
these composites.

[0019]On the other hand, there is also one document relating to multilayer
construction in diapers. WO 2005/023536 discloses an absorbent article
comprising at least one first microlayer film region having a liquid
intake function, at least one second microlayer film region having a
liquid uptake and distribution function, at least one third microlayer
film region having a liquid retention function, and at least one fourth
microlayer film region having a liquid barrier function. These first,
second, third and fourth microlayer film regions are co-extruded and
assembled with each other to form the unitary micro-layered film system.
However, these layers apparently have a thickness above the nm range and
do not assemble themselves.

[0020]Controlled release systems utilizing a homogeneous (not-layered)
matrix are also known and frequently encountered in the medical area.

[0021]WO 97/04819, as one example of this technology, relates to a medical
device for controlling a bacterial infection wherein said device
comprises a pH-sensitive polymer matrix containing a biologically active
agent, said agent being released from said polymer matrix upon pH change.
This matrix is homogenous and is not obtained by layer-by-layer
deposition of two interacting polymers. U.S. Pat. No. 5,607,417 discloses
a medical device for controlling a bacterial infection of a similar type
as described in WO 97/04819.

[0022]WO 2005/013906 discloses a pH-responsive film comprising (a) a
biocompatible, hydrophilic polymer that is positively charged at a first
pH and in electronically neutral form at higher pH; and (b) an alkylene
oxide polymer or copolymer. The film is obtained by dissolving all
components followed by solvent-evaporation film casting. It has a
thickness of about 3 to 6 mil and can be used for contraception,
treatment and/or prevention of viral infections, treatment of vaginal
infections, relief of vaginal itch, vaginal cleansing and enhancement of
vaginal lubrication.

OBJECTS AND SUMMARY

[0023]In view of the above, it is one technical object to provide an
absorbent article with an economic carrier for active agents, in
particular a controlled release system that shows the smallest possible
effect on other properties of the substrate to which the carrier is
applied.

[0024]Moreover, it is another technical object to provide an absorbent
article with a carrier for active agents, in particular a controlled
release system that is flexible and adapts to configuration changes of
the underlying substrate.

[0025]It is one further technical object to provide an absorbent article
with a carrier for active agents, in particular a controlled release
system that is suitable for treating irregular surfaces, for instance
fibers as used in many diaper products.

[0026]It is one further technical object to provide an absorbent article
with a carrier for active agents, in particular a controlled release
system that can be applied rapidly (e.g. by dipping, spraying, printing,
coating, etc.) and uniformly.

[0027]It is one further technical object to provide an absorbent article
with a carrier for active agents, in particular a controlled release
system that can be manufactured without the aid of organic solvents or
other environmentally undesired chemicals.

[0028]It is one further technical object to provide an absorbent article
with a carrier for active agents, in particular a controlled release
system that allows localizing and protecting the active agent.

[0029]According to one embodiment of the present disclosure, it is one
further technical object to provide an absorbent article with a
controlled release system that is capable of releasing the active agent
under the influence of an appropriate trigger such as changes in pH,
temperature or salt concentration.

[0030]An absorbent article such as a diaper, panty diaper, panty liner,
sanitary napkin, or incontinence device, wherein at least one part of
said absorbent article carries a film comprising at least one
monomolecular layer of a polymer having a functional group and an active
agent, in particular such an absorbent article wherein the film ("LBL
film") is obtainable by layer-by-layer (LBL) deposition of at least a
first polymer having a first functional group and a second polymer having
a second functional group capable of interacting with the first
functional group. (In the following, a reference to "LBL films" is
intended to apply equally to "films" having only one monomolecular layer,
if not stated otherwise.)

[0031]According to one further aspect, it is provided the use of a film
obtainable by the layer-by-layer (LBL) deposition of at least one first
polymer having a first functional group, in particular a polycationic
polymer and a second polymer having a second functional group capable of
interacting with the first functional group, in particular a polyanionic
polymer for releasing an active agent contained in said film upon wetting
of said film by body fluids.

[0032]The LBL films used are capable of binding an active agent
incorporated therein or deposited thereon and in this manner act as a
carrier for the active agent. According to one embodiment, the LBL film
releases the active agent in a controlled fashion. "Controlled release"
means that the active agent is not immediately released, but either
gradually and/or preferably in response to an outer trigger. LBL films,
specifically those based on polyelectrolytes of opposite charges or
alternating hydrogen donor/acceptor polymers, are for instance capable of
showing an excellent response to triggers associated with body fluids,
such as changes in temperature, pH and salt concentration (ionic
strength).

[0033]Economic use is made of the carrier polymers and the active agent
since only very small amounts are needed for LBL film formation.
Simultaneously, bulk properties of the substrate (e.g. diaper part)
carrying the LBL film are not altered more than necessary. Specifically,
important characteristics such as softness, flexibility, porosity or
absorbency will not suffer to an undesired extent. A thickness of
preferably below 1 μm provides the LBL film with the necessary
flexibility to follow movements of the underlying substrate. The LBL
technique used is moreover most suitable to treat irregular surfaces such
as those of fibers frequently occurring in absorbent products.

[0034]Further, it is advantageous that LBL technology is water-based and
allows the formation of coating films without the use of potentially
hazardous organic solvents.

[0035]The LBL film used moreover binds the active agent to that part of
the absorbent article where they are needed. This film may also exert a
protecting function against undesired influences such as body fluid
ingredients, or for instance during storage, against long-time exposure
to air or higher temperature which may enhance undesired migration
tendencies of certain active agents.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036]As "absorbent article" we understand articles capable of absorbing
body fluids such as urine, watery feces, female secretion or menstrual
fluids. These absorbent articles include, but are not limited to diapers,
panty diapers, panty liners, sanitary napkins or incontinence device (as
used for instance for adults). In some absorbent products without
absorbent layer, such as specific panty liners marketed by the present
assignee under various trademarks in connection with the product name
"Freshness everyday", the absorbent capacity of topsheet and backsheet is
sufficient to absorb small amounts of female secretion.

[0037]Such absorbent articles preferably have a liquid-pervious topsheet
which during use is facing the wearer's body. They further comprise a
liquid-impervious backsheet, for instance a plastic film, a
plastic-coated nonwoven or a hydrophobic nonwoven and preferably an
absorbent layer (core) enclosed between the liquid-pervious topsheet and
the liquid-impervious backsheet.

[0038]The part of the absorbent article carrying the film (preferably LBL
film) is preferably selected from a topsheet, backsheet, layers arranged
between topsheet and absorbent layer, such as acquisition/distribution
layers, fibers or particles used for diaper manufacture such as
cellulosic fluff pulp and/or superabsorbent particles or fibers, as
typically used as material for the absorbent layer, a waistband and leg
cuffs.

[0039]A suitable topsheet may be manufactured from a wide range of
materials such as woven and nonwoven materials (e.g. a nonwoven web of
fibers), polymeric materials such as apertured plastic films, e.g.
apertured formed thermoplastic films and hydroformed thermpoplastic
films; porous foams; reticulated foams; reticulated thermoplastic films;
and thermoplastic scrims. Suitable woven and nonwoven materials can be
comprised of natural fibers (e.g. wood or cotton fibers), synthetic
fibers (e.g. polymeric fibers such as polyesters, polypropylene or
polyethylene fibers) or from a combination of natural and synthetic
fibers. When the topsheet comprises a nonwoven web, the web may be
manufactured by a wide number of known techniques. For example, the web
may be spun-bonded, carded, wet-laid, melt-blown, hydroentangled,
combinations of the above or the like. It is preferred to make use of
apertured plastic films (e.g. thermoplastic films) or nonwoven materials
based on synthetic fibers, e.g. those made from polyethylene or
polypropylene homo- or copolymers and polymer compositions based thereon.

[0040]If present, the at least one further layer existing between the
absorbent layer and the topsheet may be made from hydrophobic and
hydrophilic web or foam materials. As "web material" we understand
coherent flat fiber-based structures of paper tissue, woven or nonwoven
type. The nonwoven material may have the same features as described above
for topsheets.

[0041]Specifically, the at least one further layer may contribute to fluid
management, for instance in the form of at least one
acquisition/distribution layer. Such structures are taught for instance
by U.S. Pat. No. 5,558,655, EP 0 640 330 A1, EP 0 631 768 A1 or WO
95/01147.

[0042]"Foam materials" are also well known in the art and for instance
describe in EP 0 878 481 A1 or EP 1 217 978 A1 in the name of the present
assignee.

[0043]The absorbent layer which may be partially or totally surrounded by
a core wrap may comprise any absorbent material that is generally
compressible, conformable, non-irritating to the wearer's skin and
capable of absorbing and retaining liquids such as urine and other body
exudates.

[0044]The absorbent layer may comprise a wide variety of liquid-absorbent
materials commonly used in disposable diapers and other absorbent
articles such as comminuted wood pulp, which is generally referred to as
air felt or fluff. Examples of other suitable absorbent materials include
creped cellulose wadding; melt blown polymers, including co-form;
chemically stiffened, modified or cross-linked cellulosic fibers; tissue,
including tissue wraps and tissue laminates, absorbent foams, absorbent
sponges, superabsorbent polymers (such as superabsorbent fibers),
absorbent gelling materials, or any other known absorbent materials or
combinations of materials. Examples of some combinations of suitable
absorbent materials are fluff with absorbent gelling materials and/or
superabsorbent polymers, and absorbent gelling materials and
superabsorbent fibers etc.

[0045]The backsheet prevents the exudates absorbed by the absorbent layer
and containing with the article from soiling other external articles that
may contact the absorbent article, such as bed sheets and undergarments.
In preferred embodiments, the backsheet is substantially impervious to
liquids (e.g., urine) and comprises a laminate of a nonwoven and a thin
plastic film such as a thermoplastic film having a thickness of about
0.012 mm to about 0.051 mm. Suitable backsheet films include those
manufactured by Tredegar Industries Inc. of Terre Haute, Ind. and sold
under the trade names X15306, X10962, and X10964. Other suitable
backsheet materials may include breathable materials that permit vapors
to escape from the absorbent article while still preventing exudates from
passing through the backsheet. Exemplary breathable materials may include
materials such as woven webs, nonwoven webs, composite materials such as
film-coated nonwoven webs, and microporous films.

[0046]Diapers (including panty diapers) preferably comprise leakage
prevention means in the form of leg cuffs such as gasketing and/or
barrier cuffs, which can carry a film (preferably LBL film).

[0047]Barrier leg cuffs are disposed adjacent each of the two longitudinal
side edges of a diaper and have a proximal edge affixed adjacent to the
longitudinal side edge and a distal edge unsecured to at least a portion
of the absorbent articles. Elastically contractible gasketing cuffs are
disposed adjacent each of the longitudinal side edges of an absorbent
article, said gasketing cuffs extending laterally outward from said
longitudinal side edges. Should exudates flow beyond the barrier cuffs,
leakage prevention is further enhanced by the gasketing cuffs forming an
additional liquid-impervious barrier around the leg or waist of the
wearer. An example of suitable gasketing and barrier leg cuffs is
disclosed in U.S. Pat. No. 4,695,278. Leg cuffs can be manufactured from
the same materials as described above for topsheets. Preferably, nonwoven
materials based on synthetic fibers are used.

[0048]To enhance the anchorage of the LBL film to hydrophobic diaper
materials it may be preferred to treat them with a thin primer and/or
subject the same to a surface modification step. It is preferred to use
primer materials that are known to show a good adhesion to hydrophobic
materials, but simultaneously can be employed in LBL technology. One
preferred primer of this type is polyethyleneimine (PEI). PEI coating
leads to a positive surface charge. Moreover, it can be preferred to
admix the active agent, e.g. skin care actives to the aqueous primer
solution.

[0049]Preferred surface modification techniques involve plasma or corona
treatment as described for instance in WO 99/001099. Both techniques
increase the hydrophilicity of nonwoven or film surfaces, preferably to
molar oxygen/carbon ratio exceeding 0,19 as described in WO 99/01099.
Plasma-treated materials which are suitable for use as liquid-permeable
topsheets are also described in U.S. Pat. No. 4,743,494 and WO 94/28568,
EP 0 483 858 A1 and U.S. Pat. No. 4,351,784. Since corona and plasma
treatment tend to introduce negatively charged groups into the surface,
it is preferred to use polycationic polymers as first layer in the
following LBL deposition.

[0050]Any part of an absorbent article can carry the nanoscalar film. The
part to be treated can be appropriately selected by a skilled person and
primarily depends on the type of active agent to be used. Skin care
agents as one example of active agents are preferably incorporated into
parts of the absorbent article that contact the skin of the wearer. As
far as diapers are concerned, these contact areas comprise for instance
the waist band, the topsheet and gasketing and/or front barrier leg
cuffs. Generally, it is preferred to apply skin care agents to the leg
cuffs, if present, and/or the topsheet of an absorbent article. LBL films
comprising odour-controlling agents can also be used in other parts of an
absorbent article, for instance below the topsheet on or in an
acquisition/distribution layer, on or in the absorbent layer, for
instance as coating of fluff pulp or superabsorbent particles, or as
backsheet coating on that side of a backsheet facing the wearer.

[0051]The LBL film can be present as continuous or discontinuous coating
on the part of the absorbent article to be treated. "Discontinuous"
coatings include the random or patterned deposition of LBL films.
Especially printing techniques are suitable for the application of
patterns.

[0052]The "LBL film" includes at least one monomolecular layer.
"Monomolecular" means in line with the common understanding of this term
in the art that the extension (thickness) of the layer essentially
corresponds to a monomolecular coverage of the treated surface with
polymer molecules.

[0053]The "LBL film" preferably has a thickness in the nanometer scale,
i.e. below 1 μm. Higher thickness values (e.g. up to 5 or up to 3
μm) can be reached if the active agent is present as large particles
as may be the case with biological material (bacterial cells or parts
thereof, e.g. lactobacillus). Preferably, the LBL film has a thickness of
less than 100 nm, more preferably less than 50 nm (e.g. less than 20 nm).
The measurement is conducted after drying the freshly deposited films at
a relative humidity of 50% at 20° C. until the film thickness has
reached an equilibrium under these conditions. Preferably, ellipsometry
is used for the measurement.

[0054]The LBL film may be composed of a single monomolecular layer
comprising one polymer having a functional group and an active agent.
This embodiment is of interest for low molecular weight organic active
agents where one layer can provide the necessary embedding of the active
agent.

[0055]Single layer films, however, are sometimes not capable of providing
a uniform coating. To enjoy the full benefits, it is therefore preferred
to provide an LBL film which is composed of two or more layers, more
preferably 2 to 100 layers, in particular 3 to 50 layers (e.g. 4 to 20
layers).

[0056]These multilayer embodiments are obtainable by a layer-by-layer
deposition of at least a first polymer having a first functional group
and a second polymer having a second functional group capable of
interacting with the first functional group. The expressions "first" and
"second polymer" are not to be understood as limiting regarding the order
of applying these polymers. Of course, it is equally possible to start
with the deposition of the "second" polymer followed by a layer of the
"first" polymer. Moreover, LBL films having more than two layers may be
formed from one or more types of a "first" or "second polymer",
respectively. To give an example, a multi-layer polyelectrolyte film does
not require the use of the same polycationic or polyanionc polymer in the
respective layers. Thus, two or more different polycationic and two or
more different polyanionic polymers can be used for film formation.
Finally, it is also possible to use mixtures of two or more polymers of
the same kind in one layer.

[0057]This layer-by-layer (LBL) deposition technique is well known in the
art of making multilayer thin films (please refer for instance to "G.
Decher and J.B. Schlenoff (ed), Multilayer Thin Films, Sequential
Assembly of Nanocomposite Materials, Wiley VCH 2003", incorporated by
reference). In line with the LBL technique, the term "layer" is not to be
understood in a strict sense of a material zone showing exclusively a
two-dimensional extension and strict boundaries to the adjacent layer.
Measurements have shown that LBL-deposited layers show a certain spread
of for instance up to seven times the average layer thickness (preferably
up to 4 times). In other words, a single monomolecular polymer layer may
penetrate into the neighbouring layers.

[0058]Nonetheless, the layering structure of these nanoscalar films and
their thickness can be confirmed by various analytical techniques
including UV/Vis spectroscopy, ellipsometry, X-ray reflectometry, neutron
reflectometry, in situ atomic microscopy (AFM), quartz crystal
microbalance (QCM), surface force measurements and others described in
"G. Decher and J. B. Schlenoff, Multilayer Thin Films". The preferred
method for determining film thickness is ellipsometry.

[0059]It is preferred that the functional group of the first, second and
possible further polymers is a polar group. As "functional group" we
understand groups that are not solely based on carbon and hydrogen atoms.
Preferred functional groups comprise at least one oxygen, nitrogen,
sulfur, phosphor, silicon or metal atom.

[0060]The interaction between the first and second functional group is
preferably based on electrostatic attraction, donor/acceptor interaction,
hydrogen bonding or specific recognition, in particular specific chemical
or biological recognition (e.g. streptavidinavidin). The polymers used
for LBL deposition preferably have a weight average molecular weight of
at least 10,000, preferably at least 50,000, in particular at least
100,000 (as for instance determined by light scattering). Generally,
higher molecular weights seem to favor LBL deposition. There is no
specific upper limit regarding the molecular weight even though, in view
of the desired use of a fully water-based coating technology, the
polymers preferably remain water-soluble.

[0061]According to one embodiment of the present disclosure, the first
polymer is a neutral polymer comprising a hydrogen bond donor ("hydrogen
bond donor polymer"). Hydrogen-bond donors are moieties that contain at
least one hydrogen atom that can participate in hydrogen-bond formation
and a more electronegative atom bound to the hydrogen atom. Examples of
these moieties include, but are not limited to, O--H, N--H, P--H, and
S--H. The moiety C--H can also be a hydrogen-bond donor if the carbon
atom is bound to another atoms through a triple bond, if the carbon atom
is bound through a double bond to O, or if the carbon atom is bound to at
least two atoms selected from O, F, Cl, and Br. This first neutral
polymer is preferably selected from polycarboxylic acid, such as
polyacrylic acid (PAA) or polymethacrylic acid, a polynucleotide, a
polymer of vinylnucleic acid, polyaminoacids such as polyglutamic acid
and poly(E-N-carbobenzoxy-L-lysine), and polyalcohols such as poly(vinyl
alcohol), and a copolymer thereof.

[0062]In this embodiment, the second polymer is preferably a neutral
polymer comprising a hydrogen bond acceptor ("hydrogen bond acceptor
polymer"). Hydrogen-bond acceptors are moieties that contain an atom more
electronegative than hydrogen that can also contain a lone pair of
electrons. Examples of such atoms include, but are not limited to N, O,
F, Cl, Br, I, S, and P. Preferred examples of this hydrogen bond acceptor
comprise a polyether, polyketone, a polyaldehyde, a polyacrylamide, other
polyamides, a polyamine, a polyurethane, a polyester, a polyphosphazene
or polysaccharide or copolymer thereof. Specific examples involve
polyethylene oxide, poly-1,2-dimethyoxyethylene, poly(vinylmethyl ether),
poly(vinylbenzo-18-crown-6), polyvinyl butyral,
poly(N-vinyl-2-pyrrolidone), polyacrylamide (PAAm), polymethacrylamide,
poly(N-isopropylacrylamide), poly(4-amine)styrene,
poly(cyclohexane-1,4-dimethylene terephthalate), polyhydroxy methyl
acrylate, poly(bis(methylamino)phosphazene),
poly(bis(methoxyethoxyethoxy)phosphazene, carboxymethyl cellulose or a
copolymer thereof.

[0063]Hydrogen bond donor polymers comprising acidic functions such as PAA
must be deposited under (typically acidic) conditions where the acidic
groups exist in their non-ionized form and are therefore available for
hydrogen bond formation. Similarly, hydrogen acceptor polymers comprising
basic functions should be deposited under pH conditions where the
hydrogen acceptor exists in its non-ionized form. This is also to be
considered when selecting a suitable combination of hydrogen bond donor
and hydrogen bond acceptor polymer. One suitable combination of hydrogen
bond donor and acceptor polymer is for instance PAA/PAAm which can be
deposited from their aqueous solution at a pH around 3.

[0064]LBL films based on at least two alternating layers of at least one
hydrogen bond donor and at least one hydrogen bond acceptor polymer are
particularly susceptible to pH changes. This property can be utilized in
controlled release embodiments. If the LBL film is for instance deposited
at a pH different from normal urine, contact with urine will enhance the
release of the active agent (e.g. one comprising a hydrogen bond donor
and/or acceptor moiety) incorporated therein. The pH difference between
the pH at which the alternating at least two layers of at least one
hydrogen bond donor and at least one hydrogen bond acceptor polymer are
deposited to the pH range of normal urine (5.8 to 7.4) is preferably at
least 0.5 pH units (≦5.3 or ≦7.9), in particular at least 1
or at least 2 pH units with increasing preference.

[0065]According to one further embodiment of the disclosure, the first
polymer is a polycationic polymer and the second polymer a polyanionic
polymer. Weak or strong polyelectrolytes may be used in LBL deposition.
In strong electrolytes such as polystyrene sulfonate, the ionisation is
complete or almost complete and does not change appreciably with pH. In
weak electrolytes such as polyacrylic acid, the charge density can be
adjusted by changing pH. Depending on the purpose of the LBL layer, it
can be preferred to use weak polyelectrolytes, which allow for a better
fine tuning of film properties. Especially in controlled release systems
it is preferred to use weak electrolytes. Preferred weak electrolytes
have pKa values of about 2 to about 10 (measured at 20° C.
with an aqueous solution of 1 weight % polyelectrolyte containing in
addition 5 mmol NaCl). Literature values for PAA and PAH are incidentally
about 5.0 and 9.0, respectively; "Multilayer Thin Films", page 134. These
polyelectrolytes may be homopolymers or copolymers wherein only a certain
percentage (for instance at least 50 mol %, or less than 50 mol %) of all
polymer-forming units carry the cationic or anionic group (Even though
this is not always mentioned in the following for the starting materials,
anionic groups in polyanionic polymers will carry a corresponding number
of hydrogen atoms and/or metal atoms and/or onium groups (e.g. ammonium)
for reasons of charge neutrality. Moreover, basic groups will be referred
to as cationic even though, strictly speaking, the addition of a protic
acid is required to develop the cationic charge. Accordingly, deposition
must proceed under pH conditions where the anionic and the cationic
charge is available for inter-layer bonding). The polyelectrolyte may
also be selected from biologically active polymers (DNA, RNA, proteins,
oligo- or polypeptides, enzymes, etc.), although controlled-release films
not including these are preferred in view of the lower stability of
biologically active polymers, their higher costs, possible side effects
during contact with the skin and the difficulty to purify these polymers.

[0066]Preferred polycationic polymers are preferably selected from homo-
or copolymers of at least one monomer comprising a functional group that
includes a nitrogen atom which can be protonated. They can have linear or
branched structures.

[0069]b) a polyallylamine homo- or copolymer, optionally comprising
modifier units (suitable modifier units of the polyallylamine are known
for example from WO 00/31150), in particular polyallylamine hydrochloride
(PAH);

[0072]e) poly(vinylpyridine) or poly(vinylpyridinium salt) homo- or
copolymer, including their N-alkyl derivatives,

[0073]f) polyvinylpyrrolidone homo- or copolymer, a polydiallyldialkyl,
such as poly (N,N-diallyl-N,N-di-C1-C4-alkyl-ammonium halide)
as shown in U.S. 2004/0047979 A1 , in particular poly
(N,N-diallyl-N,N-dimethylammonium chloride) (PDDA);

[0074]g) a homo- or copolymer of a quaternized
di-C1-C4-alkyl-aminoethyl acrylate or methacrylate, for example
a poly(2-hydroxy-3-methacryloylpropyl-tri-C1-C2-alkylammonium
salt) homopolymer such as a poly(2-hydroxy-3-methacryloylpropyl
trimethylammonium chloride), or a quaternized poly(2-dimethylaminoethyl
methacrylate or a quaternized
poly(vinylpyrrolidone-co-2-dimethylaminoethyl methacrylate)

[0075]h) a poly(vinylbenzyl-tri-C1-C4-alkylammonium salt), for
example a poly(vinylbenzyltri-methylammoniumchloride),

[0076]i) Polymers formed by reaction between ditertiary amines or
secondary amines and dihaloalkanes, including a polymer of an aliphatic
or araliphatic dihalide and an aliphatic
N,N,N',N'-tetra-C1-C4-alkyl-alkylenediamine, for example a
polymer of (a) propylene-1,3-dichloride or -dibromide or p-xylylene
dichloride or dibromide and (b) N,N,N',N'-tetramethyl-1,4-tetramethylene
diamine,

[0077]j) POLYQUAD® as disclosed in EP-A-456,467; or

[0078]k) a polyaminoamide (PAMAM), for example a linear PAMAM or a PAMAM
dendrimer such as an amino-terminated Starburst® PAMAM dendrimer
(Aldrich).

[0079]l) cationic acrylamide homo- or copolymers, and their modification
products, such as poly(acrylamide-co-diallyldimethylammonium chloride) or
glyoxal-acrylamideresins;

[0080]m) polymers formed by polymerisation of
N-(dialkylaminoalkyl)acrylamide monomers,

[0082]o) typical wet strength agents used in paper manufacture, such as
urea- formaldehyde resins, melamine-formaldehyde resins, polyvinylamine,
polyureide-formaldehyde resins, glyoxal-acrylamide resins and cationic
materials obtained by the reaction of polyalkylene polyamines with
polysaccharides such as starch and various natural gums, as well as
3-hydroxyazetidinium ion-containing resins, which are obtained by
reacting nitrogen-containing compounds (e.g. ammonia, primary and
secondary amine or N-containing polymers) with epichlorohydrine such as
polyaminoamide-epichlorohydrine resins, polyamine-epichlorohydrine resins
and aminopolymer-epichlorohydrine resins as for instance mentioned in
U.S. Pat. No. 3,998,690.

[0083]Preferred polycationic polymers are cationic or cationically
modified polysaccharides such as starch or cellulose derivatives, chitin,
chitosan or alginate, polyallylamine homo- or copolymers, polyvinylamine
homo- or copolymers or polyethylenemine.

[0084]Examples of suitable polyanionic polymers include, for example, a
synthetic polymer, a biopolymer or modified biopolymer comprising
carboxy, sulfo, sulfato, phosphono or phosphate groups or a mixture
thereof, or a salt thereof. They can have linear or branched structures.

[0085]Examples of synthetic polyanionic polymers are: a linear polyacrylic
acid (PAA), a branched polyacrylic acid, a polymethacrylic acid (PMA), a
polyacrylic acid or polymethacrylic acid copolymer, a linear or branched
polycyanoacrylate, a maleic or fumaric acid copolymer, a polyamido acid,
a carboxy-terminated polymer of a diamine and a di- or polycarboxylic
acid (e.g., carboxy-terminated Starburst® PAMAM dendrimers from
Aldrich). Examples of a branched polyacrylic acid include a
Carbophil® or Carbopol® type from Goodrich Corp. Examples of a
copolymer of acrylic or methacrylic acid include a copolymerization
product of an acrylic or methacrylic acid with a vinyl monomer including,
for example, acrylamide, N,N-dimethyl acrylamide or N-vinylpyrrolidone.

[0089]Preferably, the polyanionic polymer is selected from homo- and
copolymers of acrylic acid and anionic starch or cellulose derivatives
such as CMC.

[0090]When selecting suitable combinations (and concentrations) of first
and second polymers, such as polycationic and polyanionic polymers, the
interaction of potential candidates can be tested in solution prior to
carrying out the deposition if both film constituents are soluble in the
same solvent. When both solutions are mixed and flocculation occurs it is
a good sign that multilayer fabrication will be possible. Like a chemical
reaction, the precise structure of each layer depends on a set of control
parameters known to a skilled person, such as concentration, pH,
adsorption times, ionic strength or temperature, but in general the
processing window is rather broad.

[0091]LBL films, specifically those made from non-crosslinked
polyelectrolytes, are known to be responsive to external stimuli such as
changes in pH and salt concentration. In addition to a slight change in
temperature, these are precisely the conditions occurring when body
fluids such as urine or menstrual fluids are released. Due to the gradual
decomposition of urea, the pH of urine is slowly increased to mildly
alkaline conditions. Moreover, the salt concentration of urine (about 7
g/l NaCl plus other salts) is relatively high.

[0092]If for instance a film obtainable by the layer-by-layer (LBL)
deposition of at least one polycationic and at least one polyanionic
polymer and containing an active agent is wetted by body fluids, salt
bridges between positively and negatively charged ions located on the
corresponding polyanion and polycation chains open to form nanopores and
enhance the release of said active agent. Swelling of the LBL film
accompanies this process. To enhance the controlled release capacity of
the LBL films, it is preferred to deposit the same under "no or low salt"
conditions and/or at pH values differing from the pH of urine. "No or low
salt" conditions means that the LBL film is deposited from aqueous
solutions of the "first" and "second" polymer and optionally the active
agent (which may be of salt type) containing no other salts such as NaCl
or, if other salts are present, in a concentration below the salt
concentration of urine. Preferred low salt conditions are less than 5
g/l, more preferably less than 3 g/l, in particular less than 1 g/l of
these other salts. The pH difference to the pH range of normal urine (5.8
to 7.4) is preferably at least one pH unit (≦4.8≧8.4), in
particular at least 2, 3 or 4 pH units with increasing preference.

[0093]Although body fluids such as urine or menstrual fluids provide the
necessary concentration of salt to penetrate into the film, it has been
also found that even high salt concentrations do not completely
dissociate the polyions within the multilayer. Therefore, the LBL film
produced in accordance with present disclosure will still show the
necessary cohesion and adhesion to the underlying diaper part preventing
a complete wash off.

[0094]According to one embodiment, the LBL film having controlled release
properties comprises alternating layers of at least one polycationic and
polyanionic polymer and a (negatively or positively) charged active
agent. The charged active agent may be selected from the examples given
below. To incorporate the active agent into the LBL film the same can be
added to the aqueous solution of the polycationic polymer and/or the
aqueous solution of the polyanionic polymer. Deposition is then conducted
under conditions enhancing the formation of individual polymer layers
binding the active agent. Alternatively, the LBL film is deposited first
followed by loading the LBL film with the active agent. The latter
technique is described in "A. J. Chung and M. F. Rubner, Methods of
Loading and releasing low molecular weight cationic molecules in weak
polyelectrolyte mulitlayer films Langmuir 2002, 18, 1176-1183" for
poly(acrylic acid) (PAA), poly(alylamine hydrochloride) (PAH) multilayer
films and methylene blue dye as model system. This article and the
references cited therein describe how the loading of active agents into
LBL films and their controlled release can be enhanced. These principles
are also applicable to the present invention. Accordingly, it is
preferred to use weak polyelectrolytes. Moreover, these weak
polyelectrolytes are preferably deposited under conditions where the
polycationic polymer and/or the polyanionic polymer are only partially
ionised to provide binding sites for the later loading step. In contrast
thereto, fully ionised polyelectrolytes often form highly ionically
"crosslinked" multilayers with little or no binding sides for charged
active agents and less permeability in the loading step. If the weak
polyelectrolyte (for instance PAA at pH 2.5) is only partially ionised,
this results in a nonstoichiometric pairing of repeating units creating
relatively thick and loopy layers which are susceptible to swelling.
During the loading step, preferably at a pH higher than used for
deposition, the remaining protonated anionic groups (COOH in the case of
PAA) can act as binding site for the charged active agent. Analogously,
the opposite conditions can be used for incorporating a negatively
charged active agent into an LBL film providing basic binding sides. A
buffered solution of the charged active agent allows generally for a fast
and more uniform loading. The article by Chung and Rubner moreover
confirms that contact with high ionic strength solutions is an excellent
trigger for controlled release irrespective of the type of polycationic
and polyanionic polymer used.

[0095]According to one further embodiment, the LBL film having controlled
release properties comprises alternating layers of at least one hydrogen
bond donor polymer and at least one hydrogen bond acceptor polymer and an
active agent having at least one hydrogen bond donor moiety and/or at
least one hydrogen bond acceptor moiety as defined before. Suitable
active agents may be selected from the examples given below. To
incorporate the active agent into the LBL film the same can be added to
the aqueous solution of the hydrogen bond donor polymer and/or hydrogen
acceptor polymer. Deposition is then conducted under conditions enhancing
the formation of individual polymer layers binding the active agent.
Alternatively, the LBL film is deposited first followed by loading the
LBL film with the active agent.

[0096]As "active agent" we understand agents showing biological,
pharmaceutical and/or cosmetic activity as well as agents that fulfil or
contribute to specific functions of absorbent articles or parts thereof
such as odour control (e.g. by bacteria or pH control), skin care,
softness, absorbency, etc. The active agent is preferably selected from
odour-controlling agents and skin care agents. The active agent may be
organic (e.g. a single molecule, an organic particle or a biological
system) or inorganic (e.g. a single molecule or particle). The active
agent may carry a charge (cationic or anionic) and it may also comprise a
hydrogen bond donor or hydrogen bond acceptor moiety as defined before.
Such active agents can be selected from the following classes and
individual examples.

[0097]The active agent may further correspond to the aforementioned first
(e.g. polycationic) and/or second (e.g. polyanionic) polymer provided
that the same shows activity (e.g. odour-control or skin care) in the
sense of the present disclosure.

[0104]Depending on the polymer used for deposition a skilled person can
properly select a suitable agent from (a) to (e). These may in particular
carry a charge (cationic or anionic) under deposition conditions and/or
comprise a hydrogen bond donor or hydrogen bond acceptor moiety.

[0105]One technique to combat malodour in absorbent products is based on
the use of (a) organic bacteriostatic or bactericidal agents (in the
following referred to as "antibacterial"), which reduce the number of
odour-forming bacteria. It should be stressed, however, that not only
odour-controlling antibacterial agents can be used but also those showing
antibacterial activity regardless of the intended odour control.

[0107]According to one embodiment, polymeric antibacterial agents are
used. In line with this embodiment, the polymer is preferably an
antibacterial polycationic polymer such as chitosan or a polymer having
cationic antibacterial groups of the above-exemplified type (e.g.
biguanide, quaternary ammonium compounds). Such antibacterial polymers
are described for instance in WO 98/18330 and WO 01/17357. This
antibacterial polymer is preferably provided as top layer on an
underlaying LBL film terminated with a polyanionic polymer. Thereby, an
efficient binding of antibacterial polymers is achieved.

[0108]Antibacterial agents also include antibacterial nanoparticles of
metals, their oxides, salts, complexes, alloys and mixtures of these.
Examples of such metals include silver, zinc, gold, aluminium, copper,
platinum and palladium, silver being preferred. Throughout the present
application, the term "nanoparticle" designates particles having an
average size (diameter or longest axis in the case of non-spherical
particles) in the nanometer range, that is below 1 μm, preferably
below 100 nm, more preferably below 20 nm, even more preferably below 10
nm, for instance 1 to 5 nm.

[0109]According to one embodiment, antibacterial metal nanoparticles are
incorporated into the LBL film by providing an LBL film based on
alternating polyelectrolyte layers which include a "second polymer"
having an anionic group, preferably a carboxy group as in acrylic acid
homo- or copolymers (e.g. PAA). This LBL film is then treated with an
aqueous solution of a water-soluble salt of the respective metal, for
instance silver acetate, followed by removal of the treated LBL film from
this solution and an optional rinsing step with water. In this manner,
the metal ions, for instance silver ions will bind to the anionic groups.
Depending on the metal used, this metal-treated LBL film may already show
antibacterial properties. Bound silver ions are preferably converted to
metallic silver nanoparticles by reducing the ionic silver in a hydrogen
stream. On top of a metal-containing layer, as desired, further layers
can be applied as protective coating, preferably again by LBL deposition.

[0110]Suitable conditions for incorporating metal ions into LBL films and
the optional subsequent reduction with hydrogen are for instance
described in "P. C. Wang, M. F. Rubner and R. E. Cohen, Polyelectrolyte
multilayer nanoreactors for preparing silver nanoparticle composites:
Controlled metal concentration and nanoparticle size, Langmuir 2002, 18,
3370-3375" and "S. Joly, R. Kane, L. R. Radzilowski, T. Wang, A. Wu, R.
E. Cohen, E. L. Thomas, M. F. Rubner, Langmuir 2000, 16, 1354-1359" and
references cited therein. Preferably, a weak polyanionic polymer is
deposited in alternating layers with a weak or strong polycationic
polymer under conditions leading to partial ionisation of the polyanionic
polymer. That is a fraction of the anionic groups (for instance carboxyl
groups as in PAA) remains protonated. The acid protons can be
subsequently exchanged for metal cations. Upon reduction, zero valent
metal nanoparticles can be formed although this is not needed for most
systems such as Ag+ to develop an antibacterial effect. This technique
allows for the uniform and random distribution of metal ions or particles
(for instance Ag particles) throughout the LBL film. Repeated exchange
and reduction cycles can be used for achieving very high metal contents
in the LBL film. On the other hand, depending on the metal used, very
small amounts (e.g. at least 10-7 wt. %, at least 10-6 wt. %, at least
10-5 wt. %, at least 10-4 wt. %, based on a film that was dried as
described before) may already suffice to develop a strong antibacterial
effect. Even at very high metal contents (for instance up to 75 wt %) the
LBL layer still prevents aggregation of nanoparticles which otherwise
would be a problem. A particular advantage in view of the intended use in
absorbent articles is the firm binding of the metal ions or metal
nanoparticles in the polymer (LBL) layer. Accordingly, risks and problems
associated with inhalation of nanoparticles or skin penetration by
nanoparticles are minimized. Alternatively, the metal ions such as Ag
ions are directly deposited from an aqueous solution comprising the
polyelectrolyte polymer, preferably a polycationic polymer such as PEI as
taught by WO 2005/058199. Thereby, alternating layers of polycationic
polymer-metal ion/polyanionic polymer such as PEI-Ag+/PAA can be formed.

[0111]According to one further embodiment, an LBL film is provided on the
basis of alternating polyelectrolytes wherein the polyelectrolyte polymer
forming the outer layer has a functional group (e.g. a Lewis base
containing sulfur, phosphor or nitrogen, such as SH) capable of binding
directly to metal nanoparticles, such a silver nanoparticles. As desired,
a protective coating of further layers may be coated on this metal
nanoparticle layer, preferably again by LBL deposition.

[0112]According to one further embodiment, the antibacterial metal
nanoparticles are deposited on the substrate prior to LBL deposition of
alternating layers to fix the nanoparticles.

[0113]Odours may be classified as being acidic, basic or neutral.

[0114]Acidic and basic odours are preferably combated by pH control agents
(b). However, we wish to emphasize that pH control agents exerting no
odour control may also be used. pH control agents may for instance be
included for maintaining a pH value (3 to 7) acceptable to human skin in
and/or on the absorbent article. A suitable pH control agent thus
slightly lowers the pH of urine and can be selected from physiologically
acceptable, preferably buffering compounds. Therefore, the same compounds
as discussed below in connection with odour control can be employed.

[0115]Control agents for acidic odour have a pH greater than 7 and
typically include inorganic carbonates, bicarbonates, phosphates and
sulfates. Control agents for basic odour have a pH of less than 7. They
are preferably selected from acids having one, two or three carboxylic
acid groups, optionally at least one hydroxy or oxo group and preferably
2 to 10 (e.g. 3 to 6) carbon atoms. Control agents for basic odour
include compounds such as citric acid, lactic acid, tartaric, gluconic,
levulinic, glycolic, succinic, malic, fumaric acid, acid phophate salts
as well as boric acid and maleic acid. They can be provided as buffering
solution by adding appropriate amounts of base (e.g. NaOH or
Na2CO3) which are preferably adjusted to pH values of 4.5 to
6.0 as described in U.S. Pat. No. 3,704,034. Their odour control effect
may at least partially be also based on their antibacterial and
enzyme-inhibiting action. For instance, urease inhibitors represent one
class of suitable pH control agents.

[0116]To incorporate pH control agents into the LBL film, the polymers
constituting the same may be deposited from at least one aqueous solution
already containing these pH control agents in dissolved form.
Alternatively, the LBL film is loaded with the pH control agent after
film formation by contacting the same with an aqueous solution containing
the pH control agent under suitable conditions.

[0117]The pH control for basic odour may also be enhanced by the formation
of LBL films comprising acidic polymers. The acidic polymers preferably
represent partially neutralized weak polyanionic polymers and can be
selected from the above exemplified polymer classes. Examples of these
partially neutralized polyanionic polymers are partially neutralized
polyacrylic acid or polycationic acid. The corresponding LBL films
themselves are capable of exerting pH control, even in the absence of any
other active agent.

[0118]It should be noted that, as a rule, acidic pH control agents also
have a growth-inhibiting effect on undesired microorganism (bacteria) in
the absorbent article. This follows for instance from WO 00/35502 in the
name of the present applicant which discloses that, especially in the
presence of lactic acid-producing bacteria, pH values of 3.5 to 5.5 after
wetting are most effective in the control of undesired microorganisms and
undesirable odours produced thereby.

[0119]The most commonly utilized odour-controlling agents are
odour-absorbing or adsorbing particles (c) which are primarily used for
controlling neutral odour and preferably have a pH of approximately 7.
They can have negative or positive surface charges. Examples of these
known types of compounds include activated carbons, clays, zeolites,
silicas, starches and certain combinations thereof. Examples of such
agents are described in EP 0348 979 A1, EP 0 510 619, WO 91/12029, WO
91/11977, WO 91/12030, WO 97/46188, WO 97/46190, WO 97/46192, WO
97/46193, WO 97/46195 and WO 97/46196.

[0120]Examples of odour-decomposing catalysts (d) comprise metal or metal
oxide nanoparticles such as iron oxide, titanium dioxide, gold and
platinum nanoparticles as well as enzymes such as hydrolases, oxidases,
reductases, catalases, proteases and lipases. As known in the art, the
numbers of (particularly active) corners and edges increases sharply with
size reduction. Therefore, catalytic activity has already been observed
for various nanoparticulate materials where the corresponding bulk
material is inactive.

[0121]Odour-masking compounds (e) are typically of perfume type and can be
appropriately selected by a skilled person depending on the odour to be
masked. Odour-masking compounds include for instance those described on
page 22 of WO 02/056841.

[0122]Skin care agents are capable of imparting cosmetic, therapeutic
and/or protecting benefits to the skin of the user. They can be used to
prevent, alleviate or heal dermatitis and may also have a skin-soothing,
antiphlogistic (reduction of skin irritation), antimicrobial,
antibacterial, antiviral, astringent, wound-healing, cell-regenerating,
anti-inflammatory and/or anti-itch effect. Many skin care agents show
several of these effects at the same time so that a clear allocation to
one mode of action is often not possible.

[0123]Preferred skin care agents are based on naturally occurring active
agents (mostly from vegetable sources), or mixtures thereof as occurring
also in plant extracts. The phrase "naturally occurring active agents"
also includes their synthetic analogues.

[0124]Skincare agents can include substances which adsorb or absorb
irritating components in urine or excrements, for example clay minerals
(bentonite, kaolin, montmorillonite, etc.), silicon oxide compounds
(quartz, zeolites, water glass, etc.) or activated charcoal. The
substances are advantageously activated to be more adsorbent by means of
various treatments, for example with quaternary ammonium compounds.

[0126]Skincare agents can include pH-regulating additives of the type
described above in connection with odour control, for example, organic or
inorganic acids such as adipic acid, ascorbic acid, benzoic acid, citric
acid, malic acid, tartaric acid, lactic acid, phosphoric acid or
hydrochloric acid, or buffers made for example from said acids with
corresponding salts. They can also include polymeric acids, for example
polyphosphoric acid or polyacrylic acid.

[0127]Skincare agents can also include additions of probiotic
microorganisms, characterized by being antagonistic towards undesired
microorganisms, e.g. urinary tract pathogens or skin infection pathogens.
Examples of probiotic microorganisms which can be used are individual
strains or mixtures of several strains of lactic acid-producing bacteria
as taken from the species Lactobacillus acidophilus, Lactobacillus
curvatus, Lactobacillus plantarum or Lactococis lactis. Many lactic acid
producing bacteria such as those of the Lactobacillus family carry
negative charges on the outer cell wall and are thus suitable for
deposition with polycationic and polyanionic polymers.

[0140]Skincare agents can also include glucocorticoids, preferably of low
potency, for example hydrocortisone, or antipruritic, for example
antihistamines or local anaesthetics (e.g. lidocaine). Depending on the
type of polymer to be used for deposition, suitable skin care agents can
be selected by a skilled person from the above classes, for instance
those agents that carry a charge (cationic or anionic) under deposition
conditions and/or comprise a hydrogen bond donor or hydrogen bond
acceptor moiety.

[0142]The absorbent article is manufactured by applying the LBL film on
one part of this article. This part is preferably selected from a
topsheet, a backsheet, fibers or particles as used for absorbent article
manufacture, a waistband, gasketing and/or front barrier cuffs. The film
can be applied to a part that can come in contact with the wearer's skin,
such as a topsheet or leg cuffs if the active agent exerts beneficial
effects on the skin of the user as is the case with skin care agents or
pH control agents. Other active agents can be equally located in other
parts of the absorbent article. The respective part of the absorbent
article (e.g. diaper part) is then assembled in a known manner with the
remaining elements of the absorbent article. Alternatively, the absorbent
article or certain parts thereof are finalized prior to application of
the LBL film.

[0143]One method for the manufacture of an absorbent article comprises in
this order the steps of

[0144](a) contacting one part of this absorbent article with a first
aqueous solution of a first polymer comprising a first functional group
to form a layer of the first polymer, followed by removing said first
aqueous solution,

[0145](b) optionally rinsing said part of the absorbent particle with
water,

[0146](c) contacting said part of this absorbent article with a second
aqueous solution of a second polymer comprising a second functional group
to form a layer of the second polymer followed by removing said second
aqueous solution,

[0147](d) optionally rinsing said part of the absorbent particle with
water,

[0148](e) optionally forming at least one further alternating layer in the
same manner, wherein at least in one step the first or second aqueous
solution also contains the active agent in dissolved or dispersed form.

[0149]The expression "contacting" covers all known coating techniques.
These include the application of the aqueous solution by means of
spraying, printing and roller coating and preferably by dipping the
substrate into the aqueous solution.

[0150]As "aqueous solution" we understand solutions containing water as
main solvent by volume, preferably in an amount of more than 50% by
volume, more preferably in an amount of at least 80% by volume, in
particular at least 90% by volume. The aqueous solution may also contain
water-miscible organic solvents, such as water-miscible alcohols (e.g.
methanol or ethanol), ethers (e.g. THF) or ketones (e.g. acetone). The
inclusion of organic solvents can be utilized to control the deposition
of the first and/or second polymer and thereby the layer thickness. Under
certain conditions, mixtures of not more than 50 vol. % water and at
least one water-miscible solvent may also be useful.

[0151]Alternatively to the above method, the active agent is deposited
from a separate aqueous solution which is brought into contact with the
substrate prior to the deposition of the first layer, or after the
deposition of one, several or all layers of the LBL film, i.e. between
any of steps (a) to (d), as part of the repetition cycle (e) or at the
end of step (e).

[0152]According to one further technique for incorporating the active
agent into the LBL film, the LBL film is formed in line with the above
steps (a) to (e) before contacting the same with an aqueous dispersion or
preferably solution of the active agent under conditions suitable for
migration into the LBL film. Generally, changes in pH or ionic strength
in the environment of the LBL film are used for increasing its
permeability towards small molecules. This technique has been described
in "A. J. Chung et al., Langmuir, 18, 1176 (2002)" and the example 1 of
US 2004/0137039 with respect to poly(methacrylic acid)/polyethylene oxide
LBL films and is for instance suitable for loading LBL films based on
alternating polycationic and polyanionic polymers with charged active
agents.

[0153]If the layer adjacent to the substrate is to be formed from the
"second polymer", steps (a) and (c) have to be exchanged correspondingly.

[0154]Moreover, different types of a "first polymer" can be used in step
(a) and the repeating sequence (e) and different types of a "second
polymer" in step (c) and the repeating sequence (e).

[0155]Moreover, it is possible to fully omit at least one deposition step
for one charged polymer (e.g. (a) or (c), or one of the depositions steps
covered by the repeating sequence (e)) while replacing the same by the
deposition of active agents such as particles, biological molecules (e.g.
proteins) or systems (cells or cell fragments) having the same charge.
This has been described in WO 2004/071677 for a negatively charged
inorganic material having a thickness of less than about 10 nm. Useful
inorganic material includes platelet clays that are easily exfoliated in
aqueous solvent environments. The clays may be naturally occurring or
synthetic. Platelet-shaped aluminosilicates can also be used for
adsorbing malodours as upper or intermediate layer. Similarly, positively
charged inorganic particles could be used for substituting at least one
layer of a polycationic polymer.

[0156]One preferred biological system as replacement for one layer are
bacterial cells for instance those of lactic acid-producing bacteria
(e.g. lactobacillus and other families disclosed in WO 00/35502),
fragments thereof, bacterial spores (especially bacillus spp.) as well as
proteins, enzymes or antibodies.

[0157]There are no specific restrictions regarding the concentration of
the first polymer in the first aqueous solution and the second polymer in
the second aqueous solution. Preferably, the concentration ranges from
0.001 to 5 g/l, in particular 0.01 to 0.5 g/l. The active agent can be
present in a similar concentration.

[0158]The layer deposition can be conducted in a relatively broad
temperature range although, for reasons of convenience, film formation
typically occurs at room temperature.

[0159]It should be understood that wherever features (materials,
conditions, uses, etc.) are referred to as preferred, the disclosure of
the present application also extends to combination of at least two of
these features, as long as no contradiction arises thereby.

MORE PREFERRED EMBODIMENTS

[0160]The present disclosure is now illustrated by more preferred
embodiments. These embodiments reflect a combination of features that are
advantageously used.

Embodiment 1

[0161]A polyethylene-based nonwoven, preferably of the type as used for
topsheet manufacture, is optionally subjected to corona discharge to
create negative charges on the nonwoven surface. The (optionally
corona-treated) nonwoven is dipped into an aqueous solution of an active
ingredient or an aqueous solution comprising a mixture of an active
ingredient and a primer polymer. Non-limiting examples of the active
ingredient are skin care agents such as allantoin. Polyethylenimine (PEI)
may be used as primer polymer. The active ingredient and the primer
polymer form a first layer on the substrate.

[0162]The resulting nonwoven is then immersed alternately into aqueous
solutions of polyacrylic acid (PAA) and poly(allylamine hydrochloride)
(PAH) to deposit at least two coating layers. After each dipping step,
the nonwoven is optionally rinsed with water. After the final deposition
step the nonwoven is again optionally rinsed with water and then dried.

Embodiment 2

[0163]Cellulose fibers, for instance cellulose fibers as used in the
manufacture of tissue layers or cellulosic fluff pulp as used in the
manufacture of absorbent cores, are dipped into an aqueous solution of a
cationic polymer, for instance the afore-mentioned wet strength agents.
After draining and an optional rinsing step, the treated cellulose fibers
are dipped into an aqueous solution of an anionic polymer, for instance
the afore-mentioned dry strength agents, followed by draining the
double-treated fibers and an optional rinsing step. This scheme can be
repeated to deposit at least one further layer of the cationic and
anionic polymer. After the deposition of a cationic layer, a layer of
micro- or nanoporous zeolites is deposited on the fiber surface from an
aqueous dispersion. The resulting zeolite layer can be protected from
surrounding water and humidity in the air by depositing at least one
further layer of cationic polymer and optionally at least one anionic
polymer. Due to negative surface charges, the zeolite layer is thus
capable of fully replacing one layer of anionic polymer. Instead of
zeolite particles any other particle type having negative surface charges
can be used.

Embodiment 3

[0164]Alternating layers of polycationic and polyanionic polymers are
applied to a substrate material in the same manner as described in
embodiment 1 and 2. The substrate material is for instance a topsheet
(e.g. optionally corona-treated nonwoven or perforated plastic film) or a
cellulosic material, for instance cellulose fluff pulp as used in the
absorbent layer (optionally together with superabsorbent material) or
acquisition/distribution layer. As final cationic layer, chitosan or
modified chitosan is deposited from an aqueous solution to form an
antibacterial film.

Embodiment 4

[0165]A substrate, preferably the absorbent layer of the absorbent article
(e.g. those comprising cellulose fluff pulp and/or a superabsorbent
material) or a neighbouring layer (e.g. tissue wrap or
acquisition/distribution layer) is coated with at least two alternating
layers of a polyanionic (e.g. PAA) and polycationic polymer (e.g. PAH) in
any order from aqueous solutions of these polymers. Preferably, the
polyanionic polymer is deposited under pH conditions leaving free acidic
groups. Optionally, a rinsing step is conducted after each deposition.
The resulting coated substrate is then immersed into an aqueous solution
of a silver salt (e.g. acetate) to incorporate silver ions into the LBL
film where they bind to the acidic groups. Although this is not required
for antibacterial activity, the ionic silver atoms can be reduced in a
hydrogen stream to metallic silver nanoparticles, which are bound in the
polymer coating. One or more polymer layers can be applied as a
protective coating as desired, If the final layer was of polyanionic type
(PAA), the protective coating starts with a polycationic layer (PAH
layer) optionally followed by at least one further layer fulfilling the
alternating PAA/PAH construction principle. A more detailed description
of suitable process conditions is found in the aforementioned references
by Rubner (Langmuir 2000 and 2002).

[0166]This embodiment can be transferred to the incorporation of other
metal ions or metal or metal oxide nanoparticles.

[0167]Although the present disclosure has been described with reference to
certain preferred embodiments, it is apparent that modifications and
variations thereof may be made by those skilled in the art without
departing from the scope of the disclosure as defined by the following
claims.